I was just wondering about this same issue: of inverters being used to
support the grid. Just as charge controllers reduce their output
current as the voltage reaches absorption voltage, I was thinking that
GT inverters could do the same thing, instead of just shutting off, and
not reconnecting for at least 5 minutes.
In Hawaii, with PV penetration on the grid as high as 15%, the utility
asks us to widen the voltage operating window beyond IEEE specs, as
they've found that when they have a low voltage line condition, the PV
systems actually help, and they don't want them to shut off too soon and
add to the problem.
I could see a new generation of inverter specs beyond UL1741, that was
part of a smart grid controlled by the utility. They could extend the
operating window when needed to keep the grid more stable. As subsidies
dry up, this could be a future selling point, especially if it offered
the customer a more stable conditioned power supply. Also be nice for
the customer to get paid extra for this emergency peaking capabilities,
just like the big generating facilities. It might even make GT w/
battery backup more cost effective, if you could sell some battery
amp-hrs at $1/ kwh every once in a while.
Ray Walters
On 2/4/2012 7:05 PM, b...@midnitesolar.com wrote:
Sounds like a voltage source (and sinking) inverter to me.
These types can cause current distortion which the UL1741 / IEEE 1547
specs try to prevent.
Apparent must be able to turn that mode on and off I would imagine.
It's not too difficult to do. No wonder
they talk about micro-grids.
The old Trace SW series was a voltage source inverter, even when grid
tied and is basically why they had
to add that extra inductor box between SW and the grid when selling.
It could actually help the grid wave-
form voltage if it was distorted because of non-linear loads.
boB
On 2/4/2012 5:26 PM, Comet Systems wrote:
As I understand the issue they claim to be able to address, the
utilities often need a source of reactive power close at the system
delivery points, the customer sites, because reactive power does not
transmit well through the lines and transformers and uses up
transmission resources better used for real power. The reactive power
is used as a method of voltage control.
Therefore, it is reasonable that the utilities would pay a premium
for a reactive power source which would be close to the customers and
under their control. The idea has some merit and could be a
significant direction for solar pv, but whether an electronic
inverter can adequately generate reactive power at will, to act as a
compensation device and whether that is the highest and best use for
that power source is to be demonstrated. Interesting idea, though.
--
Chris Mason
President, Comet Systems Ltd
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